Funds are requested to partially support the 5th International Symposium on the Biology of Vertebrate Sex Determination to be held in April of 2009. This meeting has been held at 3-year intervals since its inception in 1997. The meeting is attended by the entire international field working on diverse vertebrate systems including amphibians, fish, birds, reptiles, monotremes, marsupials, and eutherian mammals, including pigs, goats, horses, mice, and humans. As it is nearly impossible to keep up with the advances made in so many diverse systems, the objective of this meeting is to exchange information, using a comparative approach to advance our understanding of the process of sex determination and sex differentiation. A great deal of collaboration came about as a result of the first four meetings: reagents were exchanged, experiments planned and new ways of looking at sex determination discussed. Approximately, 80% of the participants of the 4th symposium were junior scientists. We expect the 5th meeting to be as productive and stimulating as the previous four. PUBLIC HEALTH RELEVANCE: Sexual development during embryogenesis results in the formation of males and females that produce sperm and eggs, respectively. Birth defects in sexual development result in clinically significant abnormalities that include intersexes, common genital abnormalities such as hypospadias, infertility, and pathologies such as cancer. The proposed conference will bring together senior and junior scientists from around the world studying different types of vertebrate animals to learn more about sexual development to apply new knowledge to the treatment of sexual disorders and disease.